Hello Brian,
See my responses to your comments below, designated by ***.
Best Regards,
Joe Russeau
----- Original Message -----
From: "Brian Ellis" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, May 28, 2014 3:12 AM
Subject: Re: [TN] PCB Cleanliness Via Ion Chromatography Poll (informal)
> Let me add a couple of eurocents worth.
>
> 1. Ion chromatography is useless for incoming board testing. Far too long
> and far too expensive. By the time you have the results from a valid
> sample of a batch (say 1-5%), your board will be obsolete.
*** Again, I have to disagree that the "tool" is useless for incoming board
testing. It has two very important analytical features that make it
applicable. Those two features are selectivity and sensitivity. Now I am
not saying it is a perfect tool. Like any analytical technique it has its
limitations. However, it is has a tremendous amount of capability if it is
properly set-up and the user understands how to apply it AND understands the
material sets he/she is evaluating.
Does it take too long? Possibly, it depends (Doug just add that to my Mt.
Dew tab). It depends on what too long means. If your goal is to have an
immediate answer then yes it takes too long. I know many that utilize ROSE
to test/control/track incoming board cleanliness because it is quick and
gives an immediate answer, but when you ask them how they know the board is
clean, I often hear silence on the other end of the phone. On the other
hand, if your goal is to understand what is present on the surface of your
board and what impacts certain ions may have on product reliability, then
perhaps the time to test isn't so long. It really boils down to your goal
for testing. Also, if all your looking for are simple anions and cations,
then IC systems can churn those results out in about ten minutes (depending
on your set-up). If organics are in the sample matrix, then more time is
going to be needed to evaluate them. IC is not an immediate answer I'll
grant you that, but it gives those that are trying to understand their
residue picture more information about it.
As for expense, it can be expensive depending on who is doing the testing
and what is being analyzed. But keep in mind that part of the expense is
paying for the expertise and knowledge. I know that it is difficult to
place a price on that, but hey if it helps someone avoid a process line from
being shut down, then the expense of testing is a pittance by comparison.
>
> 2. SIR or ECM testing is useless for incoming board testing. Far too long
> and far too expensive. By the time you have the results from a valid
> sample of a batch (say 1-5%), your board will be obsolete.
*** Totally agree.
>
> 3. IC, SIR and ECM are qualification tests, unsuitable for incoming goods
> testing. Because of the chemical nature of the surface finishes, it is
> impossible to extrapolate the results obtained during qualification to
> production conditions, because there may be slight differences in the
> stoichiometry of the resins and their various treatments in board
> manufacture (or even changes of laminate manufacturer) etc.
>
*** My only disagreement with your statement above is classifying IC as a
qualification tool. I would not classify it as such. Why? Because there is
a lot of subjectivity between the experts in defining what is considered
clean and not clean. IPC-5704 helps some with incoming board cleanliness by
setting up an industry standard that has been mutually agreed upon within
committee. However, no such standard exists for assembly cleanliness and
some might be misled into thinking that IC can be used to qualify their
products. I'd say it can help in understanding the residue picture, but I
wouldn't rely solely on those results to say all is good. It provides data
into one aspect of reliability. Other testing may be required depending
upon what you are qualifying.
> 4. In my considered opinion, the *ONLY* practical test for incoming boards
> in a production environment is ICT (Ionic Contamination Testing),
> sometimes incorrectly called the "ROSE" test for historical reasons. It is
> fast, if rough and ready, and will detect the presence of most (but not
> all) of the harmful contaminants and bad stoichiometry of resins, without
> necessarily identifying them (some testers will give indications of the
> causes of problems by software analysis). Don't underestimate this
> valuable tool.
*** No comment.
>
> Brian
>
>
> On 23.05.2014 16:27, Richard Kraszewski wrote:
>> I actually sent this out on May 16th, but never got a single response.
>> Hoping that was not due to lack of interest, but rather due to the
>> TechNet being down. Hence, I think I'll try this one more time.
>>
>> I am hoping to run an informal " min straw poll " here.
>>
>> Questions stated are as follows:
>>
>>
>> 1. "Is your organization testing incoming PCB cleanliness via
>> ion- chromatography? Replies such as "YES" or "NO" will
>> suffice, but more detailed explanations are also acceptable.
>>
>>
>>
>> 2. " If testing via IC, do you use IPC -5704 Table 4.1 limits or
>> other? Replies such as "
>> IPC" or "other" will suffice, but more detailed explanations are also
>> acceptable.
>>
>> What's in it for you? I will summarize and post the results after a
>> few days of replies.
>>
>> Rich Kraszewski
>> Senior Process Engineer
>> Plexus
>>
>>
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